rpc_output test now a lager backend for testing

tests/rpc_output.erl

@@ -1,9 +1,62 @@
 -module(rpc_output).
 
 -export([confirm/0]).
+-include_lib("eunit/include/eunit.hrl").
+-compile([{parse_transform, lager_transform}]).
 
+-behavior(gen_event).
+
+%% gen_event callbacks
+-export([init/1,
+         handle_call/2,
+         handle_event/2,
+         handle_info/2,
+         terminate/2,
+         code_change/3]).
+         
 confirm() ->
+    gen_event:add_handler(lager_event, ?MODULE, []),
     io:put_chars("This is an io:put_chars/1 call"),
     io:format("This is an io:format/1 call"),
     io:format("This is an io:format/~w call", [2]),
-    lager:info("This is a lager message").
+    lager:info("This is a lager message"),
+    {ok, {LogId, Failures}} = gen_event:delete_handler(lager_event, ?MODULE, []),
+    ?assertEqual(5, LogId),
+    ?assertEqual([], Failures).
+
+-record(state, {level = debug, verbose = true, log_id = 1, failures = []}).
+
+init(_) -> {ok, #state{}}.
+handle_event({log, _Dest, _Level, {_Date, _Time}, [_LevelStr, _Location, Message]},
+             State) ->
+    check_log_message(lists:flatten(Message), State);
+handle_event({log, _Level, {_Date, _Time}, [_LevelStr, _Location, Message]}, State) ->
+    check_log_message(lists:flatten(Message), State);
+handle_event(_, State) ->
+    {ok, State}.
+    
+handle_call(_, State) ->
+    {ok, State}.
+
+handle_info(_, State) ->
+    {ok, State}.
+
+code_change(_OldVsn, State, _Extra) ->
+    {ok, State}.
+
+terminate(_Reason, #state{log_id = LogId, failures = Failures}) ->
+    {ok, {LogId, Failures}}.
+    
+check_log_message(Message, #state{log_id = LogId, failures = Failures} = State) ->
+    try
+        case LogId of
+            1 -> ?assertEqual(Message, "This is an io:put_chars/1 call");
+            2 -> ?assertEqual(Message, "This is an io:format/1 call");
+            3 -> ?assertEqual(Message, "This is an io:format/2 call");
+            4 -> ?assertEqual(Message, "This is a lager message");
+            _ -> ?assert(false)
+        end,
+        {ok, State#state{log_id = LogId + 1}}
+    catch
+        _:Reason -> {ok, State#state{log_id = LogId + 1, failures = [Reason|Failures]}}
+    end.